Choosing A Fiber Cable - Tight Buffer Cables Part 2

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This fiber optic tip is part two of tight buffer cables.  In this tip, we will look at riser cables.  Riser cables are commonly constructed by wrapping 900-micron plastic buffer fibers around a central strength member.  A layer of Kevlar is then applied over all the fibers, and an outer sheath finishes the cable.  This construction is shown in the figure.
 

The advantages of riser cables are that they are small, light weight, and inexpensive.  Since the fibers have the least amount of protection of all the cable designs, and the fibers are close to the surface of the cable, which are not as rugged as other fiber optic cable constructions.  Thus their installation requires more care than other cable designs. (I saw an installation where one riser cable was pulled across another riser cable and the friction caused the outer sheath to melt and resulted in several broken fibers.)

Riser cables are commonly used in vertical risers, hence their name. They are ideal for this application because of its lightweight; they are unlikely to encounter large polling forces or bending or crushing. They can also be used in cable trays, about ceilings, or pulled into a conduit, although in all these applications extra care is needed during the installation.

Riser cables are quite easy for direct connectorize.  The 900-micron buffer is large enough for connectors to be directly glued onto the fibers.  This provides a perfectly adequate connection for fibers that are terminated inside the patch panel or connector enclosure. This should not be used for fibers that are to be run across a desk or around a room.  If the individual fibers in a multiple fiber cable are to be separated and run to different parts of a room, the breakout or fan out cable should be used.

Money saving tip for owners: riser cables can be a cost-effective design for multiple fiber installations with about 6 to 24 fibers per cable. For reliability however they should not be used for long cable pulls or where they might be subjected to crushing forces.

Revenue generating tip for installers: riser cables can save money in the right situation, but if you want to customers to keep coming back to you, use them appropriately.  If you are looking at the difficult
installation, choose a heavier duty cable.
 

Next time: loose tube cables, the most rugged of all.  
 

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